WASHINGTON — His eyes well up without warning in private, thinking about his teenage daughters growing up. He choked back tears in public recently while delivering a eulogy for Beau Biden, the son of Vice President Joseph R. Biden Jr., who died at 46.

He let his passions show this month in a closed meeting with House Democrats, just days after blurting out an uncharacteristically affectionate greeting to a nun before a health care speech.

President Obama, whose cool, no-drama style has for years set him apart from the extroverted politicians so common in Washington, has been getting emotional lately. It has happened at the White House and on Capitol Hill as he makes the case for parts of his legacy that are at risk, like his health care law and trade agenda, or when he speaks about slain hostages, civilians killed by drones and racially motivated shootings.

Longtime colleagues say they are witnessing a more human side of the commander in chief than they have seen before.

“My takeaway was, ‘Wow — where’s this guy been?’ ” said Kent Conrad, a former Democratic senator from North Dakota, describing his reaction as he watched Mr. Obama’s eulogy this month for Joseph R. Biden III, known as Beau.

“I turned to my wife and said, ‘My God, if he’d shown those kinds of feelings, and that kind of connection to others, I think he would have had a different experience as president,’ ” Mr. Conrad said. “If he could let himself show that, he would do much better with the American people, and much better with Congress.”

When Mr. Obama made a surprise visit to Capitol Hill recently to plead with Democrats to support his trade agenda in the face of charges from labor unions and other opponents that doing so would doom middle-class workers while enriching big corporations, he veered from his normal script.

Instead of the kind of policy-heavy dissertation Mr. Obama usually offers, attendees said, he gave a more personal speech, reaching back to his days as a community organizer on the South Side of Chicago.

“It was a cri de coeur,” said Representative Gerald E. Connolly, a Virginia Democrat who listened to the president in a conference room adjacent to the Capitol. “You could really see the strain.”

Mr. Connolly said Mr. Obama was “as emotional as I’ve ever seen him get” as he told fellow Democrats that he was hurt that they would believe he would agree to a trade deal that would undercut workers and the middle class.

Days earlier, Mr. Obama had begun a health care speech with an uncommonly intimate greeting for Sister Carol Keehan, the chief executive of the Catholic Health Association of the United States and a political ally.

“I don’t know whether this is appropriate, but I just told Sister Carol I love her,” he said. It was the kind of comment his demonstrative vice president is known for making, but less often heard from the president.

It is not as if Mr. Obama is suddenly channeling Speaker John A. Boehner, Republican of Ohio, who is known for a misty eye and a quivering lip during interviews and in floor speeches. And the recent displays of emotion are not his first; the president cried while addressing staff members after his 2012 re-election, and again a month later talking about the Newtown, Conn., shooting massacre, which killed 20 young children and six adults.

But even Mr. Obama has admitted that he has been blindsided recently by fits of sadness, many of them prompted by the thought of his daughters — 14-year-old Sasha, who graduated this month from middle school, and 16-year-old Malia, who will go to college next year — growing up.

“I start tearing up in the middle of the day and I can’t explain it,” Mr. Obama told attendees at an Easter prayer breakfast in April. “Why am I so sad? They’re leaving me.”

He wiped away tears in February as he bade farewell to Eric H. Holder Jr., a confidant who served for six years as his attorney general. In April, he heaved a freighted sigh as he spoke of his grief “as a husband and as a father” about the deaths of Warren Weinstein and Giovanni Lo Porto, American and Italian hostages accidentally killed in a drone strike that he had ordered to take out leaders of Al Qaeda in Pakistan.

On Thursday, Mr. Obama’s face was grim and his voice subdued as he delivered a statement, by turns mournful and angry, about the fatal shooting of nine people at a black church in Charleston, S.C.

People close to the president say he is often unfairly tagged as apathetic simply because he does not carry on publicly about his feelings. But some also suggest that in the penultimate year of his presidency, Mr. Obama may feel more free to express himself.

“There’s a level of comfort that comes with having been in the role for that length of time, and he’s past his political life, as far as elections go,” said David Axelrod, a former senior adviser to Mr. Obama who has known him for 23 years. “That may give him a greater sense of comfort in revealing feelings and being emotive.”

Mr. Obama tends to be especially affected by anything that causes him to reflect on family, Mr. Axelrod added. He said he had often spoken with the president about how losing a child would be the worst thing that could ever happen.

That seemed apparent during Mr. Obama’s eulogy for Beau Biden — some of it delivered in a voice thick with tears as his eyes welled — and a long embrace that he shared afterward with Mr. Biden, who also lost his wife and 18-month-old daughter decades ago in a car accident that nearly killed Beau.

“This is, in many ways, a private man — he is not somebody who wears his emotions on his sleeve,” Mr. Connolly said of Mr. Obama. “That doesn’t mean he doesn’t have emotions.”